The Rugrats act out different animals. Tommy plays a wolf, but thinks Dil thought he was a dog as he makes a sound that sounds like "Doggy". Chuckie plays a cat and Phil and Lil play dogs. After Tommy yelled at Dil, Dil feels surprised and cries. Then he overhears Betty talking about Frederick and Stu says older brothers are monsters, which worries Tommy. Later, after the Rugrats' nap, Didi gives the Rugrats juice and cookies; the Rugrats eat theirs right away, but Tommy was still sleeping. Spike knocked the juice over, spilling on Tommy. Then, he shed some hair on Tommy. The Result -- Tommy thinks he's a monster, all because he thinks he hurt Dil's feelings. Meanwhile, Betty's brother, Freddie, pays a visit and Tommy stays in the playpen to avoid hurting the others, the fur and juice wash off him with the hose and then Frederick says that brothers don't stay monsters but sisters can be monsters, which relieves Tommy but scares Phil.
When Stu makes a comment about older brothers are "monsters" (referring to Drew of course), the Rugrats take him literally. So when Tommy scares Dil and Chuckie as he pretends to be a wolf, the babies begin to think that Stu might be right. Is Tommy turning into a monster? When Spike's shedding hair combines with some split juice on Tommy's body, he certainly begins to look like one! Can the Rugrats help him turn back to normal? - Description from Klasky Csupo
This episode marks the first appearance of Phil and Lil's Uncle Freddy.
When Chuckie crawls away from the playpen, along when Chuckie, Phil, and Lil look back at Tommy, the playpen was slightly open but when Tommy got his screwdriver back from Chuckie and went to open the playpen, it was closed all the way